Last month, Cook canceled two concerts on his current tour to attend to "personal family matters." A rep for Cook subsequently told People that the reigning Idol champ had missed the tour dates to spend time with his brother.

Adam Cook made a memorable appearance during his younger brother's run to the Idol crown last spring when he traveled from his home in Terre Haute, IN to Hollywood to watch a performance episode taping as a member of the live studio audience. At the time, Adam Cook was undergoing chemotherapy following his second diagnosis of brain cancer, which had spread to his spine.

He is survived by his wife Kendra and their two young children.

In addition to serving as grand marshal for the Race for Hope, Cook was part of a team that also raised $98,000 for the The Brain Tumor Society and Accelerate Brain Cancer Cure, two organizations that aid medical research on brain cancer.

"I couldn't imagine being anywhere else right now," Cook told the event's audience after revealing his brother had passed away.

"I go on stage every night and I make noise. That's my job, and it's an amazing job, and I have everybody here who voted [for me on American Idol] to thank for that. I am consistently amazed at what survivors like the people in this audience go and do... It's just amazing for me to see the results that survivors have. I lost one today, but I gained 9,000. I will be here every year that they will have me."

(Photo credit Fox)

DISCUSS AND COMMENT ON THIS STORYReality TV World now offers Facebook Comments on our stories. To post a comment, log into Facebook and then 'Add' your comment. To report spam or abuse, click the 'X' in the upper right corner of the comment box.